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In order to improve the fertilizer performance, a double-gear fertilizer apparatus was designed. Aiming to optimize the fertilizer performance, the discrete element simulation technology was used. The pressure angle of gear tooth and the interval of fertilizer wheel were taken as test factors. The coefficient of variation of fertilization uniformity was measured as test indicators, and the influence of various factors on the indicators was obtained and analyzed. The results of single factors simulation test showed that fertilizer apparatus had relatively small coefficient of variation of fertilization uniformity. When pressure angle and fertilizer wheel interval was at 15°~25° and 4~6mm, respectively. According to the results of single factor experiment, a quadratic general rotation unitized design method was conducted, and regression equations of two key structural parameters and coefficient of variation of fertilization uniformity were established. The results showed that coefficient of variation was increased at first, and then decreased with the increase of pressure angle and fertilizer wheel interval. When they were 19.52° and 4.7mm respectively, coefficient of variation of fertilization uniformity was minimum, in this case, the coefficient of variation of theoretical calculation value and simulation test value were 15.30% and 14.58% respectively, and the deviation was only 0.72 percentage point, the regression model was accurate and credible. In order to validate the regression model established by simulation test and optimization effect of structure parameters, a bench test of double-gear fertilizer apparatus with the optimized structure parameters combination of fertilizer wheel was carried out. The results showed that fertilizer discharge flow rate can be adjusted linearly by the speed of fertilizer wheel. The average coefficient of variation was 15.42%, which was basically consistent with simulation test value and theoretical calculation value. Under the same condition, the coefficient of variation of outer groove-wheel fertilizer apparatus was 20.29%. The coefficient of variation of beach test was increased by 31.58%. It obviously improved the fertilization uniformity.